This invention relates to an AC metallized film capacitor containing an ester dielectric fluid and 2 to 10% of a N,N-substituted carbodiimide to improve the capacitance retention characteristics of the capacitor.
Frequently, ester-based dielectric fluids used in AC metallized film capacitors are stabilized, e.g. against hydrolysis, by epoxides. Even when these fluids are stabilized, the capacitors impregnated with them show a capacitance loss on life testing. This loss may be caused by corona, traces of water or acids, or incomplete impregnation of wound sections.